Guidance of marine vessels

ABSTRACT

A method for controlling the cruise of an autonomous vessel incorporates using a subsystem of a payload of the vessel functional in generating locational data relating to a target. A controller for controlling the cruise control subsystems determining the bearing and the velocity of said vessel.

FIELD OF THE INVENTION

The present invention relates to guidance of marine vessels. Morespecifically, the invention relates to guidance of unmanned marinevessels.

BACKGROUND OF THE INVENTION

An unmanned marine vessel was described in PCT/IL2005/001329 from thesame applicant. Such a marine vessel can carry a variety of payloads.Such payloads may be related to any task that the vessel is to fulfill,civil, military, reconnaissance, guard tasks, or any combinationthereof. Payload on board vessels may include subsystems that relate topositioning of the vessel in relation to either a geographic grid or toa local object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart describing an exemplary sequence of stepsimplemented by a vessel which follows a target boat and instructed tokeep a specific distance from the target;

FIG. 2 is a flow chart describing an exemplary sequence of stepsimplemented by a vessel instructed to follow a specific course guided bya subsystem of the payload;

FIG. 3 is a block diagram describing the data flow from payload tovessel's guidance control system;

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The invention is typically implemented in an unmanned marine vessel, butthe invention may also be implemented in a manned vessel. Such a vessel,as discussed above, can carry a variety of payloads, some of which orsome subsystems of which can be used to aid in the guidance of thevessel. The payload utilizable in accordance with the present inventionis any appliance useful in providing locational data, i.e. data bearingdistance information to a target relative to an accepted geographicalgrid or to a local grid. In the art, optical and electromagneticequipment are used to such ends. To better explain the invention, someexamples are given in the following.

The control over the payload and vessel may be categorized in any of thethree following possible categories. The first type relates to a vesselfully controlled by a remote control unit such that the control signalsare initiated in the control unit and the response parameters are fedback to the same unit. The second type relates to an autonomous vesselfully responsible for initiating changes in sail parameters as requiredby the changing circumstances. The third type relates to a vessel havingpartial control over the cruise guidance, for example, at certain partsof the mission the control is fully managed by the control unit whereasat other occasions the mission is fully controlled by the vessel. Theautonomy is in such case directed by an algorithm stored on board thevessel or somewhere else. Typically, however it is likely that acombined control is practiced, meaning a supervised autonomy keepingsome control over the vessel.

EXAMPLE 1 Guidance to a Target

A vessel carrying an electromagnetic radiation detection system uses thepayload for guidance purposes. Systems for locating and geolocatingradiation sources are known in the art, such as the system disclosed inU.S. Pat. No. 5,719,584. Geolocating a radiating source may requireseveral receiving stations, which may require cooperation of morevessels or a vessel and a stationary station, or a combination of suchstations. If only the direction of the radiating station is ofconsequence, the payload on board the vessel may be a sufficient sourceof information for the boat maintaining a predetermined directionrelative to a target. Such payload typically detects either optical orRF signals originating in the target or reflected by it. If, however thedirection as well as the distance to the target are required forfulfilling a mission, the payload on board the vessel may not besufficient, in such cases there may be need for an additional datasource, for example from an on shore station and/or from a subsystem ofthe vessel itself. The use of a payload for electromagnetic radiationdetection can be efficiently exploited if the unmanned vessel is tofollow a specific radiation source. In such case, geolocating the sourcecan be considered of secondary importance, since the main mission is tofollow and approach the radiation source. For example, an opticaldetecting payload on board the vessel is aimed at the target. From thispoint on, the boat is to continue following a course functionallydependant upon the location of the target as viewed by the payload ofthe vessel with reference to an inertial direction. The guiding functionmay be a zero order function (i.e. a constant angle) or a higher orderfunction. The vessel maneuvers itself both as regards velocity anddirection such that the projected courses converge both with referenceto the distance to be traveled and with respect to the time scale.

EXAMPLE 2 Guidance Associated with Velocity Control

A vessel bearing a target acquisition system such as radar uses theacquisition system to guide the vessel. The vessel is instructed bywireless communication to follow a target at a specific range. The eventflow representing a velocity control of the vessel is described in FIG.1 to which reference is now made. In step 20 the vessel receives anoperational instruction to stay at a specific distance D from a target.At step 22 the acquisition payload on board the vessel acquires thetarget, and at step 24 the distance to the target is measured bypayload. At decision step 26 if the distance measured is smaller thanthe required D, velocity is decreased at step 28. If the distance is notsmaller than D, velocity is increased in step 30. In a next decision, atstep 32, the vessel verifies whether an operational instruction is inforce. If it is still in force, the distance is measured and so on.Measuring of distance to the target is accomplished using the rangefinder of the payload on board the vessel, either in a supervised manneror automatically.

EXAMPLE 3 Guidance Associated with Course Control

A vessel carrying an electro-optic acquisition system uses the payloadfor guidance purposes. The output signal of a bearing finder, such as aresolver implemented in the payload is used to guide the vessel. Toexplain this, example reference is made to FIG. 2. The vessel receivesinstruction as to the course it should follow in step 60. The vessel isto change to course D if it is not currently sailing in that direction.In step 62 the payload orients itself relative to the target. Indecision step 66 the relative measured bearing to the target is comparedto the one received in the instruction. If the measured relative bearingis not smaller than the required D, then the vessel is steered left instep 70. If the measured relative bearing is smaller than D, the vesselis to steer right in step 70. Subsequently, the vessel verifies whetheran operational instruction is in force in step 74, to resume courseupdate if required.

Target acquisition systems require relating the acquisition payload tothe target such that a direction to the target, (e.g. a boat) from thepayload is established. This may also be referred to as a line of sight.The payload on a vessel implementing the invention is therefore expectedto establish a direction (line of sight) to a target, once the target isacquired. For a guidance system in accordance with the invention it isconvenient to relate to direction as issued by the acquisition system.This may be interpreted in using the line of sight as an axis ofreference. This is implemented geometrically by generating a localcircular coordinate system, also known as polar coordinate system, withrespect to which the vessel is oriented. In such a grid the direction isreferred to as an angle from the reference axis (relative to thevessel), in this case line of sight to the target. Thus, a targetbearing 0 means cruising in the direction towards the target, and anyother degree would mean a deviation from that direction. A changeablecourse, whether related to a reference axis directed to a target or to aglobal bearing, would mean referring the vessel to different angles ofthe deviation from any reference axis. Either an automatic algorithm ora manual input can be used for managing such a course. Typically, thevessel can cruise in a constant course deviating from the direction tothe target at a specific angle, etc.

EXAMPLE 4 Guidance Associated with Combined Course and Distance Control

A vessel is required to change both course and velocity with respect toa target in its maneuvers in the water. Such changes may be implementedin the water by applying control over both the drive and steeringsystems. In FIG. 3 to which reference is now made, a schematic blockdiagram is shown describing the data flow between subunits in a vesselimplementing the invention. Signals 86 from the payload subsystem whichcontain locational data are fed into navigation processor 88 of thevessel. In the vessel, task manager 90, a program that calculates thecourse and velocity modifications, is to be implemented by vessel cruisecontrol 92 in order to achieve a desired maneuver with respect to thetarget. The instructions are interpreted by a vessel cruise control intomechanical parameters of the appropriate vessel's mechanical subunits.

Such mechanical subunits are typically the rudder (course modification)and the engine (velocity modification), together performing thenecessary maneuvers to acquire a specific course in the water, eithermomentarily or continuously. In jet propelled vessels, the coursecontrol and maneuvering are performed by jet steering. Some vessels,typically small ones, employ a steerable external engine, which can bemanipulated for both changing velocity and changing bearing.

1. A system for controlling the cruise of a vessel comprising: asubsystem of a payload of said vessel functional in generatinglocational data relating to a target; a controller for controlling thecruise control units determining bearing and velocity of said vessel. 2.A payload for controlling the cruise of a vessel as in claim 1 furthercomprising an interpreting system of said vessel for accepting signalsof said payload of said vessel and for moderating them to be accepted bysaid controller.
 3. A system for controlling the cruise of a vessel asin claim 1 wherein said vessel is an unmanned vessel.
 4. A system forcontrolling the cruise of a vessel as in claim 1 wherein said cruisecontrol units selected from a group consisting of a rudder and anengine, and any combination thereof.
 5. A system for controlling thecruise of a vessel as in claim 1 wherein said cruise control units areselected from a group consisting of a jet steering subunit, an engineand an external steerable engine, or any combination thereof.
 6. Amethod for guiding a vessel comprising: using a subsystem of a payloadof said vessel for obtaining locational data; determining at least acourse of said vessel in relation to said locational data.
 7. A methodfor guiding a vessel as in claim 6 wherein said vessel is guidedrelative to a reference axis of a polar coordinate system, wherein saidreference axis is a line of sight to a target.
 8. A method for guiding avessel as in claim 6 wherein said vessel is guided relative to adistance from a target.
 9. A method for guiding a vessel as in claim 6wherein said vessel is autonomous.
 10. A method for guiding a vessel asin claim 6 wherein said vessel is fully remote controlled.
 11. A methodfor guiding an autonomous vessel with respect to a target vessel,wherein said autonomous vessel keeps a functionally dependent courserelated to the location of said target vessel with a constant inertialreference.
 12. A method as in claim 11 for guiding an autonomous vesselwith respect to a target vessel, wherein said autonomous vesselmanoeuvres itself to keep said course, functionally dependent upon thelocation of said target.